Processing pigment dispersions



Fatented July i3, 193'? No Drawing.

Application June 9, 1934,

Serial No. 729,913

8 (Claims.

The present invention relates to the utilization of sogasoids in theformation of disperse systems in which finely divided solids areuniformly dispersed in a selected dispersion medium.

The dispersion medium may be a gas, a vapor, a

liquid, a solid or a plastic substance, or it may be ,a mixture of anyor all of them. Also, it may be a mixture of a dispersion medium in anyof its own phases or in a mixture of the phases. For m example, adispersion medium such as camphor can well serve in three phases, i. e.as solid, as liquid and as vapor. This is true particularly during themodification of one phase into the other in either direction. If solidcamphor is first melted into its liquid phase, it in turn may bemodified into the gas or vapor phase and the latter condensed into theliquid phase and finally settling into a solid. This is an example ofthe maxim Natura non saltat, nature makes no jumps.

The present invention has for its object the utilization of sogasoids toform intermediary dispersoids, the dispersion medium of which is a partor is compatible or is a constituent of the end product in which thefinely divided solids, i. e. the disperse phase (the solids) of theintermediary dispersoid, are to be incorporated.

In my prior and co-pending application, Serial 590,319, filed February1, 1932 (now United States Letters Patent No. 1,965,764), I havedisclosed processes for the production of disperse systems in which thefinely divided solids are initially dispersed in an aqueous dispersionmedium and are thereafter transferred to an organic medium either by (a)admixing the initial aqueous dispersion and the organic medium, andthereafter distilling off the aqueous medium, or by (1)) creating,converting and breaking emulsions formed by the two immiscible liquidscomprising the dispersion medium, or by (c) heating the organicdispersion. medium and adding the aqueous dispersion of the solidsthereto at such a rate as to vaporize the aqueous medium upon contacttherewith.

In another of my prior and co-pending applications, i. e. Serial579,662, I have disclosed processes for the production of dispersoids inwhich finely divided solids constitute the disperse phase dispersed innon-aqueous dispersion media. In my United States Patent No. 1,955,738,applied for January 18, 1929, under Serial 333,523 I have disclosed andclaimed processes for the utilization and conversion of. aqueousmixtures of pigments as finely divided solids into organic dispersoidsin which the pigments constitute the disperse phase.

Depending upon the characteristics of the finely divided solids as wellas the dispersion medium, dispersoids, whether aqueous or nonaqueous,are obtained with more or less efiorts and my processes and methods asdisclosed in aforesaid applications and patent enable the dismrsionexpert to choose the more economical route and technically leastresisting way when making compositions.

In the processes disclosed and claimed in my said co-pendingapplications and patent, the finely divided solids such as pigments areprepared in a liquid initial intermediary dispersion medium, which isthereafter displaced by a final or ultimate displacing or replacingmedium.

The present invention utilizes so-called sogasoids which are systemsconsisting of a solid phase suspended in a gaseous or vapor phase ormedium, as defined in Hackhs Chemical Dictionary. Examples of sogasoidsare dry powders and dusts or smokes where gases or vapors are retainedby fine solid particles through the force of adsorption. Commercialcarbon black, lamp black, acetylene black, bone black, zinc oxide, are afew of such sogasoids. Cabot states that carbon black may occupy onlyfive percent of its own apparent volume, the rest being adsorbed air andair free to move between particles. The amnity between gases or vaporsand finely divided or porous solids is very great. One only needs toconsider the attraction for poisonous or other gases by the activatedcarbon particles in gas masks. Lamb and Coolidge, who carried outmeasurements, have estimated that adsorbed gases may be under a pressureof many thousand atmospheres.

I propose to utilize such sogasoids to facilitate the incorporation offinely divided solids such as abrasives, fillers, colors, pigments,lakes and the like into vehicles such as oils, resins, waxes, cellulose,cellulose compounds, and rubber, or solutions of emulsions thereof toform products useful in the manufacture of or as adhesives,insecticides, leather, leather finishes, artificial leather, printingink, soap, candles, cosmetics, varnishes, varnish stains, oil stains,putties, wood finishes, metal finishes, fiatting compounds, fioor wax,sealing wax, coating compounds, plastics, thermo-plastics, lubricants,rubber goods, tires, paint, paint-enamels, celluloid, lacquer,photographic films, oicloth, linoleum, etc. For convenience, all of saidproducts will be hereinafter referred to as consumer products.

. tion I obtain uniform and stable In the specific instance ofdispersing pigment as finely divided solids in a suitable medium forplastic or coating compositions, it is common practice to grind thepigment particles before attempting to incorporate such particles in thedispersion medium and thereafter to grind both pigment and dispersionmedium to accomplish the dispersion of the, pigment particles in thevehicle. In either case, the grinding may afiect the unground color ofthe pigment. Also, it has been found that the grinding of the pigment inthe vehicle does not result in creating a stable dispersion of thepigment particles in the vehicle or a dispersion which even under idealconditions is as uniform as is desired for many purposes. By theprocesses of my present invendispersions of pigment particles in thevehicle with a greater degree of uniformity than has heretofore beenpossible to achieve. In the present process I first disperse the pigmentparticles in a gas or vapor, and in so doing I eliminate the necessityfor grinding of the pigment in and into the vehicle. In some instances Imay use a ground pigment or may even preparatively grind the pigment, sothat the invention, while making possible the use of an ungroundpigment, is not limited thereto.

Further and additional objects of my invention will more readily appearin the perusal of my specifications and examples. Aside from theeconomical advantages over present methods, I desire to emphasize thatthe merits of my invention are reflected by the excellent quality ofproducts when made in accordance with my teachings and that they derivetheir distinctive pleasing appearance and superior eiiectiveness fromthe uniformity and evenness of the nature and characteristics of theirinitial intermediate dispersion. This mark of uniformity of appearanceand superior effectiveness which distinguishes the individual batch orrun is again reflected in any number of successive batches or runs whichin their turn prove that variations in manufacture may be eliminated bymy teachings which exclude the human element by depending upon thephysical or chemical constants of the componentsutilized in processesand apparatus as disclosed.

The quality of the above enumerated products depends largely also uponcomplete saturation of the incorporated solids by and with thecompounding element which thus facilitates their even distribution inthe end or consumer products. Since it is technically far easier andmore economical to obtain finely divided solids.completely saturated,impregnated or surrounded with a gaseous medium such as vapors than itis to saturate them by impregnation with oil or viscous or plasticvehicles after they (the solids) have been dried, i. e.. in the form ofdry powders, I have therefore-chos v n and desire to employ these solidsdispersed in a gaseous medium such as steam or vapor or air, etc., incontravention of present manufacturing processes.

Certain pigments, for example carbon blacks, result from the partialcombustion of a gas. In their dry state such pigments exist in adispersed condition in the gaseous products of combustion or air. Such arse system may consist of finely divided soliving gas as the dispersionmedium. and also the rsing agent can be a gas, e. g. mm: car dlomde,

carbon monomde, suipiiurous acid, or the vapor of p azeotropic-..1-,:.-. alcohol, toluene, water,

mixtures, acetylene, acetic acid, etc. Such disperse systems, whenformed with a liquid dispersion medium, are similar physically to foams,lather, froth, or sprays, while if formed with a gas as a dispersionmedium are similar physically to smokes or mists. For example,commercial carbon black is a disperse system of a solid in a gas, 1. e.solid carbon particles are dispersed in an atmosphere of air, carbondioxide and carbon monoxide, which gases are formed during thecombustion of natural or other hydrocarbonaceous gases for themanufacture of carbon blacks, lamp blacks, acetylene blacks, and similarcommercial varieties of carbon, such gases being retained by adsorptionin the carbon particles. To make a dispersion of carbon black in wateror otherwise produce disperse systems of carbon blackand a. liquid,either aqueous or non-aqueous, requires dispersing agents. Such agentsalso may consist of gases or vapors, such for example as ammonia gas orpyridine vapor or vapors of the organic amines.

By the process embodying the present invention I utilize gaseousdispersions of solid particles and extend such dispersions by addingmore of the gaseous dispersion medium thereto, which has the eifect ofdiluting such dispersoids. I have discovered that the so-called dry pigments existing as powders, or fine dust particles, may be considered asdispersed in air. To such dispersions I add more air to extend or dilutethis initial dispersion to a predetermined point. I thereafter fdefiatepersion by use of a replacing or displacing medium which is compatiblewith the dispersion medium of the end product.

I shall now illustrate processes embodying my invention by way ofseveral examples thereof.

Example I Production of carbon black puZp.I n a closed barrel which isprovided with an open inlet for steam under low pressure, are placedfifty pounds of commercial carbon black or lamp black. In the barrel ispreferably inserted a heating coil through which steam circulates inorder to obtain a temperature in the barrel sufiiciently high to preventexcessive condensation when open, steam is let in. A suitable quantityof ammonia in the form of ammonia-water or as gas or salts from whichammonia may become liberated is placed in the barrel. The steam inlet isthen opened, and steam is blown into the barrel. After a short time itwill be noticed that the volume which was occupied by the dry carbonblack is considerably reduced and the carbon black is wetted and forms apulp in which the solid particles are dispersed in a. portion of thecondensed steam and aqueous ammonia. The vapor pressure of the ammoniais used to facilitate the wetting process and contributes directly tothe obtaining of the carbon black in the form of a pulp. In place of theammonia and steam, pyridine vapors may be used, in which event aftercondensation oi the pyridine gas, the resulting pulp consists of carbonblack dispersed in pyridine as the pulping medium. The gaseous initialdispersion medium of the commercial carbon black has been replaced anddisplaced in one case by water and ammonia vapors and in the other caseby the pyridine vapors in a very eflective man- 'ner. Merely sogcommercial carbon black in liquid water or liquid pyridine will not havethis efiect because of the difl'erence in volume be the gaseous distweenthe liquid phase and the gaseous or vapor phase of pyridine.

The present invention thus utilizes the great affinity of-finely dividedsubstances for gases or vapors to effect dispersion of such solids inselected media.

Phosphorous pentoxide is a very hygroscopic substance, i. e. it drawsmoisture out of moist air and is therefore used in desiccators.Phosphorous pentoxide, however, in form of smoke, i. e. when dispersedin air, passes through water. This is due to the film of air being sostrongly adsorbed that the water cannot reach the phosphorous pentoxide.Thus in the process of the present invention, I may utilize phosphorouspentoxide dispersed in air in place of the ammonia and steam or thepyridine vapors of the example. Here we have a similar situation as inthe case of emulsions. We have emulsions of the water-in-oil type andthe oil-in-water type. A dyestuii very soluble in water cannot color anemulsion of the water-in-oil type because the dye does not reach thewater to become dissolved because the water is protected by the oilparticles. In the phosphorous pentoxide and water exam-- ple, the air ison the outside like a coat, thus preventing the water from dissolvingthe phosphorous pentoxide. According to the laws of physics. gases arecompletely miscible in and with each other. The laws of vapors aresomewhat similar to the gas laws in this respect and for this reason theVapors of the pyridine in this example mix perfectly with the adsorbedgas film around the carbon particles, and when condensation of thepyridine vapors into the liquid phase takes place the air escapes andthe liquid pyridine can reach the exposed carbon particle to completelywet it and thus forms a pulp or the intermediary dispersoid ready forconversion into the final and ultimate end or consumer product. In thecase of phosphorous pentoxide the adsorbed air film would be violentlyliberated by adding the water in the vapor phase, i. e. steaming Theblack pulp resulting from the example above may be further processed bymy processes disclosed in applications Serials 590,31Q, (now UnitedStates Letters Patent No. 1,965,764), 579,- 662, or my United StatesPatent 1,955,738. Such a pulp of fifty pounds water and twenty-fivepounds carbon black, may, for exampie, be placed into a kneading machinewith twenty-five pounds of alkali-cellulose and worked into a. pulphaving carbon black and alkali-cellulose as solid components and waterfor the pulping medium. At this stage the entire mass shows an alkalireaction because of the partial dissociation of the alkali-cellulose inwater. The resultant, dispersion is particularly adapted to color paperpulp to make black or gray paper without risking contamination of thebeater room or the entire mill with carbon black dust as when usingcarbon black in theform of dry powder.

Example If Production of colored xanthates.--Place the above describedpulp into a closed and tight kneading machine of the type described inmy co-pending application Serial 590,319 (now United States LettersPatent No. 1,965,764) and while kneading blades are kept going add fivehundred cubic centimeters of carbon bi-sulphide. The alkali-cellulose inthe pulp is thereby transformed into the xanthate which, with therequisite amount of alkaline water, will form a smooth paste, in thiscase colored black with carbon black.

I have found that such a pulp or paste serves very well to color rubberlatex.

While I have cited specifically the use of zinc oxide or carbon blacks,any alkali resistant pigment such as ultra-marine, chrome-oxide, sulphur dyes, vat dyes, a large group of diazo colors, may be used in placethereof to give the desired color to the finished product.

From the foregoing it becomes clear that the gaseous dispersoids or thesogasoids of this invention are very voluminous. This quality is nottroublesome when such sogasoids need not be shipped out are furtherprocessed where manufactured. Carbon black makers, in order to reducethe normal volume of carbon black resulting from combustion processes,reduce this volume by compression. When such compressed blacks are to beincorporated into end products, the compounder complains about theincreased difficulties he has to overcome when attempting to dispersecompressed blacks in the final composition.

Example HZ Method of obtaining a carbon black rubber pulp with tolueneas the pulping medium.-Fifty pounds of commercial carbon black are bymeans of an air blower (Connersville type) moved and circulated in aclosed tank of three hundred gallon capacity. Also in this case aquantity of ammonia gas (ten pounds) will promote the air dispersion ofthe pigment. In a closed tank of one hundred gallon capacity, of uprightcylin drical shape like a hot-water tank, place four hundred fiftypounds of a three percent rubber cement and agitate by means of ahigh-speed mixer of the propeller type. The contents of the threehundred gallon tank, 1. e. the sogasoid of fifty pounds carbon black,are now blown through this rubber cement. The air escapes through theopening of the one hundred gallon tank which is connected with acondenser to recover some toluene vapors carried along by the escapingair. The diluted commercial carbon black (diluted with air) is trappedin the rubber cement with which it forms the intermediary dispersoid,which now may be converted into the ultimate end product by the methoddisclosed in my co-pending application Serial 579,662.

In place of rubber I may use gutta-percha, nitrocellulose or a xanthatesolution or rubber latex, which latter is protected from coagulation bythe ammonia contents which served as dispersing agents when the carbonblack was circulated with air in the three hundred gallon tank.

It will be observed that these sogasoids function only as anintermediary dispersoid for they cannot serve permanently. One onlyneeds to think of the smoke screens laid by a battleship or an airplaneto see that such dispersoids are unstable and of comparatively shortduration.

' In the processes disclosed in my aforesaid applications and patent itwill be observed that during the distillation processes therein"disclosed, gaseous or vapor dispersions of this present application maybe formed. Before the vapors in these processes reach the condenser theyof course fill all the available space in the apparatus and consequentlyduring this period there are dispersions formed of finely divided solidsdispersed in the vapor atmosphere of the apparatus, but also in thiscase such dispersions are only of intermediary character for the veryobject of the process is to remove the vapors and replace them with areplacing medium. Nevertheless, during the replacing process gaseousdisperse systems are formed, the gaseous or vapor phase of which may bethe vaporsof alcohol, water, toluene, solvent naphtha, azeotropicmixtures, pyridine, acetic acid, organic amines, etc.

I claim:

1. A process for producing a dispersion of carbon black in a dispersionmedium liquid under normal atmospheric temperature and pressure, whichcomprises dispersing the carbon black in its dry state in gaseousammonia and steam, and thereafter condensing the ammonia and steam tothe liquid phase whereby the carbon black is dispersedin and wetted bythe admixed ammonia and water solution as the dispersion medium.

2. A process for producing a dispersion of carbon black in a liquiddispersion medium which comprises dispersing the carbon black in its drystate in gaseous pyridine, and thereafter condensing the pyridine to theliquid phase whereby the carbon black is dispersed in and wetted by thepyridine solution as the dispersion medium.

3. A method of processing carbon black to reduce its bulk and facilitateits incorporation into selected dispersion media which comprisesdispersing carbon black in its dry state to form a sogasoid in which thecarbon black is the dispersed solid and in which a vapor of a mediumliquid under normal conditions of temperature and pressure andcompatible with and obtaining as a part of the selected dispersionmedium is the suspension medium, and thereafter condensing the vapor toits liquid phase whereby the bulk of the carbon black in the sogasoid isreduced and the carbon black particles are dispersed in and wetted bythe condensed liquid.

4. A process for dispersing finely divided solids in selected mediaefiective to wet said finely divided solids, which comprises forming aninitial dispersion of the solids in their finely divided solid forms bysubjecting the solids to agitation in the selected medium in its vaporphase to increase the bulk of the mass and the dispersion of the solidsin the vapors of said medium, and thereafter reducing the bulk of thedispersion hy condensing the dispersion medium to form a liquiddispersion medium in which the finely divided solids are dispersed andwetted.

5. A process for stabilizing dispersions of finely divided solids, whichcomprises forming an initial sogasoid comprising the finely dividedsolids as the disperse phase and a suspension medium maintained in itsvapor phase, said suspension medium existing normally as a liquid atatmospheric temperatures and pressures and possessing the property ofwetting said finely divided solids, and thereafter condensing the vaporphase of the suspension medium, whereby the initial sogasoid is reducedin bulk, the finely divided solids are wetted thereby and the dispersionof the finely divided solids therein is stabilized.

6. A process for dispersing finely divided solids in a liquid mediumcapable of acting as a dispersion medium for the finely divided solids,which comprises the steps of dispersing a suitable quantity of thefinely divided solids in a gaseous dispersion medium, thereafterdisplacing the gaseous dispersion medium with the vapors of the saidliquid medium, and thereafter condensing said vapors to disperse thefinely divided solids in said medium in its liquid phase.

'1. A process for dispersing finely divided solids in liquid mediaacting as a dispersion medium therefor, which comprises dispersing asuitable quantity of the finely divided solids in the vapors 01 aselected dispersion medium which exists as a liquid at normalatmospheric temperatures and pressures, and thereafter stabilizing theformed dispersion by condensation of the vapor phase of the dispersionmedium and its conversion to the liquid phase in which the-finelydivided solids are dispersed.

8. A process for dispersing finely divided solids in a dispersion mediumcapable of wetting said solids, the process comprising the steps ofdispersing finely divided solids in a gaseous dispersion medium to forma sogasoid, and thereafter replacing the gaseous medium of the sogasoidwith substantially the same volume of vapors of a dispersion mediumliquid at atmospheric temperatures and pressures, and thereaftercondensing the vapors of said medium to form a liquid body in which thefinely divided solids are wetted and dispersed.

mm C. DE STU-BNER.

